Semiconductor lasers have many advantages, such as being small and inexpensive as well as having low power consumption and a long operating life, and have been used in many applications, such as a light source for optical recording, a light source for communication, a laser display, a laser printer, and a laser pointer. Laser displays and laser printers generally use a scanning method. In a currently used semiconductor laser scanning method, the orientation of a laser beam of a semiconductor laser is controlled by using an external and additional element such as a polygon mirror, a MEMS (micro-electro mechanical system) micro mirror, or a unit using an acousto-optical element. However, adding such a scanning mechanism to a semiconductor laser makes it difficult to reduce the size and improve working speed and durability.
Given this factor, the inventors of the present invention have been providing a photonic crystal surface emission laser capable of changing the emission direction. The photonic crystal surface emission laser used in Patent Document 1 is a combination of two photonic crystal layers with different periods. This photonic crystal surface emission laser emits a laser beam in the oblique direction with respect to the emission plane (which will be hereinafter referred to as an “oblique beam”) based on the principle that a spatial beat is generated due to the frequency difference of the standing waves of light formed in the two photonic crystal layers. Increasing the frequency difference increases the emission angle (inclination angle) of the emitted laser beam.
The emitting direction controllable photonic crystal surface emission laser of Patent Document 1 uses the change in the output angle caused by the frequency difference. In the emitting direction controllable photonic crystal surface emission laser, the period of the modified refractive index area of one photonic crystal layer is fixed, whereas that of the other photonic crystal layer changes according to the position within the same layer. This structure enables an emission of an oblique beam at a different emission angle according to the position of the laser oscillation.
Adding an emission direction control function to the semiconductor laser itself can achieve a reduction in size and increase the working speed and durability. This should create new application fields such as a portable device with a built-in laser display and an optical interconnection between electronic chips.